Congenital stromal corneal dystrophy

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Congenital stromal corneal dystrophy is an inherited eye disorder that primarily affects the clear layer that covers the front surface of the eye (cornea). Affected individuals have multiple corneal opacities, which are damaged areas that cause the cornea to appear cloudy or opaque rather than transparent. These corneal opacities form in the thickest layer of the cornea (stroma) and are typically present in both eyes (bilateral) from birth or soon thereafter. The corneas of affected individuals may also be thicker than normal and have an irregular surface. These corneal changes lead to a loss of visual acuity, which can impair a person’s ability to see clearly. Without treatment, visual acuity can worsen over time.

Congenital stromal corneal dystrophy is often associated with additional eye abnormalities, including eyes that do not look in the same direction (strabismus) and "lazy eye" (amblyopia). Less commonly, affected individuals may have involuntary eye movements (nystagmus) or increased sensitivity to light (photophobia).

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Congenital stromal corneal dystrophy is caused by variants (also called mutations) in the DCN gene. This gene provides instructions for making a protein called decorin, which is involved in the organization of collagens. Collagens are proteins that strengthen and support connective tissues such as skin, bone, tendons, and ligaments. Collagens also play an important role in the cornea. Bundles of collagen called fibrils must be strictly organized for the cornea to be transparent. Decorin helps ensure that these collagen fibrils are the right size and are regularly spaced.

The variants in the DCN gene that cause congenital stromal corneal dystrophy lead to the production of an abnormal version of decorin that does not function as it should. Researchers believe that this abnormal protein accumulates in the cornea, which causes the cornea to become cloudy. The accumulation of abnormal decorin may also lead to the other eye abnormalities seen in people with congenital stromal corneal dystrophy.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. Some cases of this condition likely result from new (de novo) variants in the gene that occur during the formation of reproductive cells (eggs or sperm) in an affected individual's parent or during early embryonic development. These affected individuals typically have no history of the disorder in their family.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Congenital stromal corneal dystrophy is rare; only a few affected families have been reported in the medical literature.

Understanding terms used in the source

These definitions explain medical words used above. A definition is not evidence that another condition is present, and it does not predict how a symptom will develop. Ask the clinician which terms apply to the actual examination or test result.

Corneal dystrophy

The term corneal dystrophy embraces a heterogenous group of bilateral genetically determined non-inflammatory corneal diseases that are restricted to the cornea.

Photophobia

Excessive sensitivity to light with the sensation of discomfort or pain in the eyes due to exposure to bright light.

Strabismus

A misalignment of the eyes so that the visual axes deviate from bifoveal fixation. The classification of strabismus may be based on a number of features including the relative position of the eyes, whether the deviation is latent or manifest, intermittent or constant, concomitant or otherwise and according to the age of onset and the relevance of any associated refractive error.

Amblyopia

Reduced visual acuity that is uncorrectable by lenses in the absence of detectable anatomic defects in the eye or visual pathways.

Nystagmus

Rhythmic, involuntary oscillations of one or both eyes related to abnormality in fixation, conjugate gaze, or vestibular mechanisms.

Which doctor should you see?

The suggested department for discussing Congenital stromal corneal dystrophy is Ophthalmology, with a ophthalmologist as the relevant type of clinician. Ophthalmologist; paediatric services for children as appropriate.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Which part of the eye or visual pathway is affected?
• What change in vision requires immediate contact with the eye service?
• What are the aims and alternatives of any proposed eye treatment?

Treatment discussions and follow-up

Where the source describes treatments, these are an overview of possible care, not a prescription for an individual. Ask which option applies to the confirmed diagnosis, what benefit is expected, what adverse effects to watch for and how progress will be assessed. Availability, approvals and local practice can differ from the country described in the source.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.